Electric gauge



Feb. 20, 1945. R, MEsTAs ELECTRIC GAUGE Original Filed Sept. 14, 1937 `Bob 3.a

A TTOANEKS.

Patented Feb. 20,1945

ELECTRIC GAUGE RlcardoMestas, Los Angeles, Calif., assignor to Kobe, Inc., Huntington Park, Calif., a corporation of California original application september 14, 1937, serial No.` 163,807. Divided and this application January 2,1942, Serial No. 425,423

, 1s claims. (ci. 3347178) This invention relates to electric gauges. Present-day manufacturing methods require a high degree of precision in the machining of parts of fabricated articles. A satisfactory gaugev must not only accurately respond to extremely small deviations in dimension, but--such deviations must; be amplified and visually indicated to the operator. And the gauge for practical success must be simply and inexpensively constructed, and compactV and convenient to apply to the object gauged.

An object of my invention is to provide a gauge with these qualities of accuracy, sensitiveness, economy of cost, compactness,and convenience. The gauge is of the electric type and utilizes the mechanical movement ofA ar gauge l element as it follows the surfaceto be gauged to vary the air gap of a magnetic circuit, which,

the gauge capable of insertion within tubular in turn, causes variations in current, which Y variations can be accurately indicated by a suitable meter.

One of the objects' of my invention is toprovide electrical apparatus which will amplify and accurately indicate the deviations in dimension of the gauged object, and which at the same time will comprise a minimum of electrical elements of simple and standard construction.

Another object is to provide an electrical `apparatus which will measure the electric potential of alternating current coils by a direct current galvanometer, so as to secure the advantage of directional indications and a high degree` of sensitivenessof this type of potential meter.

Another object of my invention is to provide an arrangement of electrical devices which will measure deviations in dimension of the gauged object without being aected by incidental variations in voltage of the current from the'source of supply.

Another purpose is to provide such an arrange-v ment of electrical elements that a varying potential may be produced by a few small parts conveniently located in a small housing which may be applied in restricted spaces;

Another object is to provide a gauge housing which will be small, will have suitable mounting of the electrical and mechanical parts, and which will protect these parts from mechanical injury and from dirt and other foreign matter.

Another object is to provide for ready assembly and dismantling of the electrical and mechanical parts and for convenient accessibility for their inspection and repair.

Still another object is to afford a gauge which may be readily inserted within the internal bore of long casingg andother cylindrical objects of which it is desired to gauge the internal dimensions.

construction and arrangement ofv parts by which I utiliseA pieces of standard pipe for rendering objects of relatively great length, and by which the conductor wires of an electric gauge may be disposed in protected positions within the pipe and vother gauge parts.

The drawing and description are of one em'- bodiment of my invention. They illustrate and describe' a gauge for measuring the internal diameter of 'cylindrical casings, sleeves, or tubing 'such `as are used in the manufacture, among other things, of pumps, and which must be machined'with a high degree of accuracy and a minimum of tolerance. It will, however, be readily appreciated that, by obvious alterations in the design of the gauge housing and gauge element,` some of the principles of my invention, as outlined in some of the claims, can be embodied in a. gauge for measuring the external diameter of tubing or pipes, as well as in gauges of many kinds for detecting deviations in plane surfaces', and for measuring the thickness and other dimensions of fabricated parts.

In the drawing,

Figure 1 is a perspective view of a gauge embodying my invention;

Figure 2 is a longitudinal cross-sectional view taken along the line 2,-2 of Figure 1; Figure 3 is a longitudinal cross-sectional view of the gaugehandle taken along the line 3-3 Figure 6 is -a cross-sectional view along the line 6 6 of Figure 2; and

Figure 7 is a diagram of the electrical cir.-

l cuits of the gauge.

The invention provides a gauge housing i0 including a cylindrical body Il formed with an internal chamber I2 which is rectangular in cross section, as viewed in Figure 5. Cooperating with the body II in forming the housing IU is a tighttting cover I3 which is removably secured to' the body by screws I3a to close the chamber I2, this cover I3 providing an arcuate external face conforming with the body Il to provide a generally cylindrical housing I adapted to be inserted within a piece of cylindrical tubing I4 which, in this example. is the article to be gauged. The body II and cover I3 form a dirtproof housing rfor the mechanically movable parts and the electromagnetic elements of the gauge.

Two elongated guide means in the form of lugs or shoes I5 are rigidly secured by screws I5a in two grooves I6 formed longitudinally in the exterior wall of the body at an angular interval of about 120 from each other. A movable gauge element or work-contacting means is formed by a plunger I'I slidably mounted in a sleeve I8 which is rigidly secured to the cover I3, and this plunger is disposed in a radial plane angularly midway between the guide means I5. 'I'his plunger is reciprocally movable longitudinally along a radial line of the gauge housing I0, and is thus moved by variations in the bore diameter of the tubing, I4 or by elevations or depressions in the internal face I9 of the tubing.

A spring 20, seated in a recess in the sleeve I8, bears upon the lower face of a rounded inner head 2| of the plunger I1, and holds it at all times resiliently in contact with the under face of one end 22a of an electromagnetic armature 22. This armature comprises a movable element and carries a pin 22c pivoted in two soclrets22dl through a small angle under the action of the plunger I'I. By this construction, the plunger or gauge element and the armature are placed in mechanically operativeY relationship.

'I'he underside of the other end 22h of the armature has a bearing engagement with an engagement means shown as a hollow cylindrical plunger 24 slidably mounted in a sleeve 25 which is rigidly secured to the cover I3, all in a manner similar to the assembly of the plunger I1, and similarly provided with a spring 26 tending to velevate theplunger 24, which is held inr constant resilient contact with the armature end 22h. 'Ihe spring 2S, being of greater strength than spring 20, acts to hold the guide means I5 and plunger I'l in constant sliding contact with the internal wall of the tubing or sleeve to be gauged, overcoming the gravity eifect of the weight of the gauge when it is used horizontally and with the movable plunger I1 disposed at the bottom of the gauge. At the same time, the action of the spring 20 permits the plunger I'l to rise and fall with variations in the diameter of, the tested article, and thereby to slightly oscillate the armature 22. 'I'he plungers Il and 24 tend to move the armature in opposite directions of rotation. vAdjustable threaded stops 39, mounted in the body II, serve to limit the movement of the armature. Y

A laminated magnetic core 21, with the general coni'lguration or shape of a capital letter E, is fastened Aby screws 21a to the inner wall of the cover I3. About the middle leg 28 of this core is disposed a primary coil 28a connected with a source of alternating current through conductors 28h in a cable 29,' as shown diagrammatically in Figure 7. The two outside legs 30, 30.' of the core are surrounded respectively .by

tor 42.

two identically-formed secondary coils 30a, 30h connected additively in series with each other. The core and primary and secondary coils constitute a three pole electromagnet, and the two secondary coils in cooperation with the primary coil, when the latter is energized, constitute two sources of electric potential. 'I'hree conductors 33, 34, and35, lead from these secondary coils through the cable 29 to the outside. Conductor 33 is connected to the outer terminal 3l of one coil; conductor 35 is connected to the outer terminal 32 of the other coil; and conductor 34 is connected at 36 to the conductor 36a. which is the series connection between the two secondary coils. To obviate tensile stress upon the conductor leads, they are secured to terminals 31 retained by an insulating conductor terminal plate 38 mounted upon the inner wall of the cover I3.

The armature 22 is formed with a downwardlyprojecting arcuate boss 53, with its rounded lower face 5I concentric with the pivot pin 22a upon which it is mounted. The axis of this pin is immediately above and in the transverse central plane of the core leg 28, which is formed at its upper end with a mating arcuate surface 54, which preferably contacts or nearly contacts the surface 53. The axis of the pin is also perpendicular to the central longitudinal plane of the core base and legs. By virtue of this mounting of the armature, the air gap between the core leg and the central portion of the armature throughout its range of oscillatory movement is either of zero or a very small and constant magnitude.

A handle 40 formed with a bore 40a therethrough is threadedly secured to a pipe 4I of any desired length, depending upon the length of the tubing or casing to be gauged, which pipe is, in turn, threadedly engaged with a handle connec- This connector is joined to the gauge body Il by means of a flexible joint, shown as comprising a flexible pipe or tube 43, to which the connector and a neck 43a of the body are both secured by clamps 44 and 45, respectively, the clamp 44 providing a forward end loosely telescoping with the neck 43a to permit limited flexing between the body II and the elements 4l), 4I, and 42. The conductor cable 29 leads from the conductor terminal plate 38 in the chamber I2 through a longitudinal axial bore 46 formed in the body II and communicating with the chamber I2, then through the flexible tube 43, and a similar bore 42a in the connector 42, then through the pipe 4I and bore 40a in handle 40 to the source of current and to the indicating apparatus. These several bores and tube and pipe openings are in continuous and successive registry.

Referring again to Figure 7, the five conductor wires of the cable are indicated by the numerals 28h, 28D, 33, 34, and 35. Between conductors 33 and 35 are connected asymmetrical impedances, shown as two half-wave rectiflers 4B and ilV of equal impedance, with the anode of rectier 46 connected by a series connection 48 to the cathode of -rectier 41. Conductor 34 leads from the secondary coil series connection 36a at 36 to a sensitive galvanometer 5I and conductor 52 leads thence to the series connection 48 between the two rectiers.

, In the operation of the measuring device, the gauge body is inserted within the casing, tubing, or other cylindrical work object to be measured. When, as normally, the internal diameter of the `work is correct, the air gap 46 between the arme... ture end 22a and the leg 30 of the E-shaped core 21 is equal to the air gap 48a between the armature end 22b and the leg 30. The electromotive force induced in secondary coil 30a is then equal to that induced in secondary coil 3012i Since the rectiers 46 and 4l are electric devices ofeclualv impedancel the potential at 36 is equal to thatat 46 and no current ilows through the galvanomcore base, core legand armature end 22h, in

accordance with the well known principle that the reluctance of a magnetic circuit varies directly with the length of` the air gap or gaps in the circuit. Since induced electromctive force varies directly with the magnetic ilux, the induced electromotive force in secondary coil 30a is then greater than that in coil 38h. Since there has been no change in the relative impedance of the rectiiiersl a difference in potential then exists between points 48 and 36 and a small current flows through the galvanometer.. By reason of the action of the rectiiiers, this current is direct current, and as direct current galvanometers are very sensitive, I gain the objective of a high degree of amplication through the use of the rectiiiers.

These rectiers 46 and 4l perform a double function in the operation of the gauge. They each provide impedance in that they afford internal resistance to the flow of current in the direction in which they are designed to permit such current flow. They also prevent any ilow of cur'- rent in the opposite direction, with the result'that the current flowing through them is a direct current with a potential which varies from zero to a maximum with the same frequency as the alternating current impressed upon the primary.

-Since they are connected anode to cathode, there is a -pulsating flow of current through both of them from terminal 3i to terminal 32 and always in that same'direction. Since the internal resistances pf the two rectiiiers bear a constantfratio to each other which, in the embodiment shown and described herein, is equality and since this ratio of resistances is the same as the ratio of potentials normally generated in the secondaries 30a and 30h, it is obvious that, when the ratio of these two potentials varies from the normal, the current which passes through rectifier 46 is either more or less than thev current which passes through rectifier 41, and the dilerence is represented by the` current which flows through wires 34 and 52 and the galvanometer 5I, which may be in either direction, depending upon which of the coils 36a and 30h generates the greater potential.

It is obvious that the indicator needle of the galvanometer records the extent of the movement of the plunger I1, and itis a simple matter of calibration to design the mechanism to indicate in linear units the exact measurement of the movement of the pliuiger. When the plunger moves inwardly, an opposite set of conditions causes the galvanometer needle to move in the opposite direction. The armature 22 thus acts as a means for unbalancing the potential applied across the galvanometer terminals.

without departing from the principle of my invention. It is also apparent that modiilcations can be made in the electrical and magnetic features of the device within the scope of my invention. For example, instead of passing alternating ycurrent through the primary coil to energize the secondaries, the primary coil may be connected to a .iource oi' any other type of pulsating ycurrent or current of rapidly-varyingpotential.

Thus, direct current in combination .with an interrupter may be used. .1

I have described the secondary coils 3a-and 30h as identical and, therefore, in conjunction with the energized primary coil 28a, these coils are sources of normally equal potential. And, I have described the rectiers as having the same impedance relative to each other. It is apparent, however, that, if the two secondary coils are designed to normally impress two electric potentials bearing to each other any other definite ratio than equality, and the two rectifiers are designed to have impedance values bearing to each other the same definite ratio as that of the normallyimpressed potentials, the gauge will operate as before, and it is to be understood that equality of potential and impedance is used only as one possible convenient and preferred illustration of. such a definite ratio.

It is also apparent that, if I provide means for varying the-impedancefof the circuit between the f points 3| and 48 of Figure '7, relative to the im,-

pedance between points 48 and 32, instead of providing means for varying the relative potentials of coils 30a and 30h, the gauge will operate properly, and that it is within the scope ofmy y invention to vary either the relative potential or It has already been pointed out thatv the me- Y relative impedance, which in either case will vary the eective potential between series connections 33a and 48. means is provided for varying the impedance in the galvanometer circuit including the connections 34 and 52 so that the impedance betweenpoints 36 and 48 through the galvanometer is:A

always the same. y

There are a number of electrical vmeasuring gauges which depend upon the variation of a magnetic circuit when the length of the air gap in-v the circuit is varied. Most of these instruments measure the change -in a eld of a coil when the reluctance of the vmagnetic circuit is varied by a changing air gap. A constant alternating current potential is applied to the coil and the current which flowsthrough the coil will then be a function of the air gap. Any variation of the applied electromotive force also varies the current, with no change in air gap, so that a device of this kind, in order to function satisfactorily,

- must be supplied with a source of potential which is extremely constant. For use on ordinary lighting circuits, this requires some form of voltagel I regulator ahead of the instrument.

A gauge constructed in accordance with my inated in the two secondary coils respectively will increase and decrease correspondingly but, otherf It will also be observed that no factors being unchanged, the ratio between these two potentials will remain constant and such variation in the potential applied to the primary coil will notv be indicated by the meter.

This application is a division of my appli-cation, Serial No. 163,807, led September 14, 1937, now Patent No. 2,268,956.

I claim as my invention: l

l'. In an electric gauge, the combination of a gauge housing comprising a body providing a chamber opening on the exterior of said body and 4a cover removably secured to said body to close said chamber; work-contacting means extending from said chamber to a position outside said housing; means for translating a change in position of said work-contacting means into a corresponding electrical change, said means including a stationary member in said chamber and a movable member in said vchamber and operatively connected to said Work-contacting means; means for securing ,said stationary member to said cover to be removable therewith; and means secured to said cover for guiding the movement of said movable member relative to said stationary member whereby said movable and stationary members are removable together from said chamber upon removal of said cover.

2. In an electric gauge, the combination of: a gauge housing comprising a body providing a chamber opening on the exterior of said body and a cover removably secured to said body to close said chamber; work-contacting means extending from said chamber through said cover to a Dosition outside said housing; means for translating a change in position of said work-contacting means into a corresponding electrical change, said means including a stationary member in said chamber and a movable member in said chamber and operatively connected to said work-contacting means; means for securing said stationary member to said cover to be removable therewith; and means secured to said cover for guiding the movement of said movable member relative to said stationary member whereby said movable and stationary members and said work-contacting means are removable together from said chamber upon removal of said' cover.

3. In an electric gauge, the combination of: a gauge housing comprising a body providing a chamber opening on the exterior of said body and a cover removably secured to said body to close said chamber; a plunger extending from said chamber through said cover to a position outside said housing; an electromagnetic core secured to said cover; an armature; means for mounting said armature for movement relative to said'core to form a variable ux path, said means being secured to said cover to be removable therewith; and means for operatively connecting that portion of said plunger inside said chamber with said armature to create changes in reluctance of said ux path in response to movement of said plunger.

4. In an electric gauge, the combination of: a. gauge housing comprising abody providing a chamber opening on the exterior of said body and a cover removably secured to said body to close said chamber; a work-engaging plunger extending from said chamber through said cover to a position outside said housing; an armature in said chamber; means removable with said cover for movablymounting said armature in "a gauge housing comprising a4 body providing a ture; an engagement means bearing against said armature; and means for biasing said engagement means in a vdirection tending to move said armature in opposition to said means for biasing said plunger.

5. In an electric gauge, the combination of:

chamber opening-on'the exterior of said body and a. cover removably secured to said body to close said chamber; a work-engaging plunger extending from said chamber through said cover to a position outside said housing; an armature in said chamber; means removable with said cover for movably mounting said armature in such such position that said plunger bears thereposition that said plunger bears thereagainst; means for biasing said plunger for movement into pressural contact with said armature; an engagement means bearing against said armature; means removable with said cover for guiding said engagement means; and means for biasing said engagement means .in a direction tending to move said armature in opposition to said .means for biasing said plunger.

6. In an electric gauge, the combination of: a gauge housingcomprising a body providing a chamber opening on the exterior of said body and a cover removably secured to said body to close said chamber; an armature in said chamber; pivot means for pivoting said armature in said chamber for movement in either one of two directions; a Work-engaging plunger extending from said chamber to a position outside said housing and positioned to engage said armature on one side of said pivot means; means for resiliently urging said plunger into engagement with said armature to exert thereon a moment tending to pivot said armature in one direction; an engagement'means in said chamber and positioned to engage said armature on the other side oi said pivot means; and means for resiliently urging said engagement means toward said armature to exert thereon a moment tending to pivot said armature in an opposite direction.

7. In Aan electric gauge, the combination of a gauge housing comprising a body providing' a chamber opening on the exterior of said body and a cover removably secured to said body to close said chamber; a variable-reluctance means including an varmature in said chamber; pivot means secured to said cover for pivoting said armature in said chamber for movement in either one of two directions; a work-engaging plunger extending from said chamber to a position outside said housing through said cover and positioned to engage said armature on one side of said pivot means; resilient means acting between said cover and said plunger for resiliently urging said plunger into engagement with said armature to exert thereon a moment tending to pivot said armature in one direction; an engagement means in said chamber and positioned to engage said armature'on the other side of said pivot means; and resilient means acting between said cover and said engagement means for resiliently urging sard engagementmeans into engagement with said armature to exert thereon a moment tending to pivot said armature in an opposite direction whereby said armature is urged to a normal position by said resilientr means and whereby said armature and said resilient means are removable from said body as a unit with said cover.

8. In an electric gauge, the combination of a gauge housing comprising a body providing a chamber opening on the exterior of said body and a cover removably secured to said body to removably secured to said body to close said i close said chamber; an electromagnetic core providing a base secured to said cover and providing three aligned arms extending inward into said chamber; pivot means secured to said cover adjacent the central one of said arms; an armature extending across said aligned arms and pivoted in said pivot means to present a substantialy ly constant-reluctance flux path between said armature and said central arm and two variablereluctance ftux paths between said armature and the two outside arms of said core which last-named iiux paths vary oppositely upon movement of said armature in a given direction; a work-engaging plunger extending from said chamber through said cover to a position out side said housing; and means for mounting said plunger for engagement with said armature and `for bodily removal from said chamber with said cover.

9. In an' electric gauge, the combination of a gauge housing; an E-shaped magneticv core mounted in said housing and providing a central leg and two outer legs; va primary coil positioned around one of said legs;`a secondary coil positioned around another of said legs; an armature pivotally mounted in said housing with its axis of oscillation adjacent and in the central transverse plane of said central leg and perpendicular to the central longitudinal plane of said core traversing said legs; a movable gauge element in mechanically operative relationship with said armature; and conductors leading from saidgauge housing and electrically connected to said primary and secondary coils.

10. In an electric gauge. the combination of a gauge housing; an E-shaped magnetic core mounted in said housing and providing a central leg and two outer legs; a primary coil positioned around said central leg; two secondary coils positioned respectively around said two outer legs; an armature pivotallymounted in said housing with its axis of oscillation adja.

cent and in the central transverse plane of said central leg and perpendicular to the central longitudinal'plane of said core traversing said legs; a movable gauge element providing one end in contact with one end of said armature, the other end of said gauge element being disposed outside said housing to engage the work to be' gauged; means for resiliently holding said gauge element in contact with said armature; and resilient .means operatively connected to the other end of said armature for urging same in a direction to .force said otherv end of said gauge element against the work to be gauged.

11. In an electric gauge, the combination of: a

gauge body formed with a chamber; a cover for said internal chamber removably secured to said body; an electromagnet mounted on the inner wall of said cover; a movable armature mounted on said cover within said chamber; a gauge element movably mounted with respect to said cover and projecting therebeyond to contact the article to be gauged, said gauge element being in mechanically operative relationship with said armature; aconductor terminal plate carried by said cover inside said chamber; conductors leading from said electromagnet to. said conductor terminal plate; and conductors' leading from said conductor terminal plate to a position outside said body.

chamber, said body providing a bore communieating between said chamber and the exterior A of said body; a handle means; a flexible joint operatively connecting said body and said handle means for permitting limited motion therebetween, said handle means providing a passage; electric means in said chamber; means for varying said electric means in response to changes in dimension of the article to be gauged; and con',

'ductors extending from said electric means 'through said bore and through said passage of said handle means.

13. A combination as defined in claim 12, in which said ilexible joint comprises a flexible tube joining said handle means and said body and through which said conductors extend.

14. A combination as defined in claim`12, in which said flexible joint comprises a flexible tube joining said handle means and said body and v through which said conductors extend, said body providing a neck extending into said flexible tube, and means extending from said handle means along the outside of said exible tube to a position adjacent said neck to limit the flexing of said tube.

15. In an electric bore gauge, the combination of: a gauge housingvformed with a longitudinal bore; a gauge element movably mounted with respect to said housing and adapted to contact an internal surface of the work to be gauged; an electromagnet mounted in the housing;- means in mechanically operative relationship with the gauge element and said electromagnet to vary the electromagnetic relationship of said electromagnet; a handle connector formed with a bore therethrough; a exible tube secured to said housing and said connector atits respective ends and with its two end openings in registry with said housing bore and said connector bore respectively; a gauge handle formed with a bore; a pipe detachably connected to said gauge handle and said handle connector at its respective ends and with its two end openings in registry withthe handle bore and connector bore respectively; t

and electric conductors connected to the electromagnet and leading successively through the housing bore, ilexible tube, connector bore, pipe, and handle bore to outside points.

. 16. A combination as defined in claim 2, in which said work-contacting means is disposed ona gauge housing comprising a body providing a 12. In an electric gauge for gauging the size chamber 'opening on the exterior yof said body and a cover removably secured to said body to close said chamber; work-contacting means exs tending from a position outside said cover through said cover and journalled with respect to said cover; means for translating a change in position of said work-contacting means into a corresponding electrical change, said means including a stationary member in said chamber formed of magnetic material and a movable armature formed of magnetic material and cooperating with said stationary member in forming a variable-reluctance flux path, the inner end of said work-contacting means being operatively associated with said armature; and means secured to said cover for movably mounting said armature to` move relative to said stationary member to vary said flux path upon movement of said work-contacting means whereby said ar- `mature is removable with said cover.

18. A combination as denned in claim 12, in. I

which said ilexible joint comprises a flexible tube joining said handle means and said body and through which said conductors extend, said body providing a neck extending into one end o! said tiembla-tube and said handle means providing a neck extending into the other end of said ilex- 

